Solid-solid phase change materials (SS-PCMs) are attractive candidates for thermal energy storage (TES) owing to their intrinsic shape stability, yet their widespread application remains limited by the lack of design rules linking the molecular structure to phase-transition properties. Here, we present a comprehensive study of layered hybrid chlorometallates, (C n H 2n+1 NH3)2MCl4 (M = Cu, Mn, Zn; n = 6-16), as tunable SS-PCMs. For that, 15 compounds (M = Cu, Mn, Zn; n = 6, 7, 12, 13, 16) were prepared, and their low-temperature (LT) forms were studied by single-crystal XRD and vibrational spectroscopies. By a multitechnique approach, involving calorimetry, temperature-dependent infrared, and Raman spectroscopies, and combined in a single synchrotron experiment temperature-dependent X-ray absorption spectroscopy (XAS), total scattering/Pair Distribution Function (PDF), and powder XRD (PXRD) analyses, we evidenced the impact of both parameters (M and n) not only on the LT structures but also on the thermal properties and on the high-temperature (HT) structures. Especially, we evidenced that although materials based on octahedrally (here Mn and Cu) and tetrahedrallly (here Zn) coordinated cations share many common features in their LT forms (alternating organic-inorganic layered structures, alkylammonium chains parallel to each other, and supramolecular organic-inorganic interactions of the same nature and strength), their HT phases strongly differ, especially at a medium range distance. This comprehensive study is not only of fundamental interest but will also help to address questions, such as the shaping and mechanical integrity of these SS-PCMs upon thermal cycling that need to be answered prior to their integration into practical devices for next-generation TES.

The ban on the use of hexavalent chromium in the protection process for food-grade tinplate has led to the development of a new passivation process called CFPA (Chromium-Free Passivation Alternative). Nevertheless, its corrosion performance is lower than that of the original process. The objective of this work is to thoroughly characterize the 555-CFPA layer in order to identify the origin of the adhesion and corrosion weaknesses observed. To achieve this, XPS spectroscopy in conventional and image mode and STEM HAADF imaging combined with EELS spectroscopy were used. A "ridge-valley" nano-roughness following the rolling patterns was observed. The thickness of the passivation layer is dependent upon its location and varies from single (similar to 8 nm) to double (similar to 18 nm). In the valleys, the passivation consists of a gradient of transition metal oxides or even (oxy)fluorides and a polymer on the surface, arranged on a protective layer of tin oxides. On the ridges, the thinner passivation layer consists of a single nano-layer of oxides. Its lateral distribution is very heterogeneous, even leading to the formation of nano-clusters at the extreme surface. Indeed, the chemical heterogeneity in passivated tinplate leads to variations in chemical potential at the surface, which could lead to different responses to corrosion and weakened steel protection.

The rise of the electronic age sparked a quest for increasingly faster and smaller switches, since this element is ubiquitous and foundational in any electronic circuit to regulate the flow of current. Mott insulators are promising candidates to meet this need as they undergo extremely fast resistive switching under electric field initiated by an avalanche phenomena. However, the nature of the final switched state is still under debate. The spatially resolved micro-X-ray Diffraction imaging and micro-Raman experiments carried out on the prototypal Mott insulator (V0.95Cr0.05)(2)O-3 show that the resistive switching is associated with the creation of a conducting filamentary path consisting in an isosymmetric compressed phase without any chemical or symmetry change. This strongly suggests that the avalanche initiated resistive switching mechanism is inherited from the bandwidth-controlled Mott-Hubbard transition just like the laser induced insulator to metal transition recently studied in the same system. This discovery may hence ease the development of a new branch of electronics called Mottronics.

Despite its excellent plasmonic properties, silver is prone to degradation under atmospheric conditions, which can reduce the performance of silver-based Surface-Enhanced Raman Scattering (SERS) sensors. To address this issue, we explore the ability of protective dielectric layers to improve durability, cleanability, and reusability of SERS substrates using silver nanoparticle chains capped with thin layers of aluminum or silicon oxides. This paper shows that a 3 to 10 nm thickness effectively shields the silver nanoparticles, with 5 nm being found as a good compromise for protection while maintaining a high SERS signal of bipyridine molecules. Experimental results demonstrate that silicon oxide-capped silver nanoparticles maintain their plasmonic properties remarkably well over 8 months and even 18 months for aluminum oxide-capping, which shows cleanable and reusable characteristics with solvents like ethanol and water.

Harnessing the luminescence potential of Cu(I) complexes in aqueous media is typically hindered by their poor photostability and altered properties. Here, we report the synthesis, engineering and morphological characterization of a hydrophobic homoleptic copper(I) complex entrapped into silica nanoparticles, Cu-I@SiO2 (where "Cu -I" designates [Cu(2,9-diiodo-1,10-phenanthroline)2]+), as a promising stabilisation strategy towards watercompatible, Cu(I) complex -based luminescence. The polyether chain -decorated nano -objects are spherical with an average diameter of ca. 10.8 +/- 1.9 nm. Upon dispersion in water, clear solution -like suspensions were obtained. Significantly, the aqueous suspensions photo -luminesce (Clem = 5x10-4) upon excitation through the Metal-to-Ligand Charge -Transfer transition (MLCT) of the embedded copper(I) complexes. In contrast, the corresponding silica -free molecular complex dissolved in an aqueous environment revealed fully quenched emission. Finally, the use of Cu-I@SiO2 suspensions as luminescent probes is reported, first by assessing their potential use as electrochemiluminescent probes, and second by monitoring the photoluminescence from CuI@SiO2 in the presence of whole blood.

With the widespread use of batteries, their increased performance is of growing in importance. One avenue for this is the enhancement of ion diffusion, particularly for solid-state electrolytes, for different ions such as lithium (Li+) and magnesium (Mg2+). Unraveling the origin of better cation diffusion in confined ionic liquids (ILs) in a polymer matrix (ionogels) is compared to that of the IL itself. Ionic conductivity measured by electrochemical impedance spectroscopy for ionogels (7.0 mS cm(-1) at 30 degrees C) is very close to the conductivity of the non-confined IL (8.9 mS cm(-1) at 30 degrees C), that is, 1-ethyl-3-methyimidazolium bis(trifluorosulfonyl)imide (EMIM TFSI). An even better ionic conductivity is observed for confined EMIM TFSI with high concentrations (1 m) of lithium or magnesium salt added. The improved macroscopic transport properties can be explained by the higher self-diffusion of each ion at the liquid-to-solid interface induced by the confinement in a poly-vinylidenedifluoride (PVDF) polymer matrix. Upon confinement, the strong breaking down of ion aggregates enables a better diffusion, especially for TFSI anion and strongly polarizing cations (e.g., Li+, Mg2+.). The coordination number of these cations in the liquid phase confirmed that Li+ and Mg2+ interact with the polymer matrix. Moreover, it is a major result that the activation energy for diffusion is lowered.

The current use of TiO2 nanoparticles raises questions about their impact on our health. Cells interact with these nanoparticles via the phospholipid membrane and, in particular, the phosphate head. This highlights the significance of understanding the interaction between phosphates and nanoparticles possessing distinct crystalline structures, specifically anatase and rutile. It is crucial to determine whether this adsorption varies based on the exposed facet(s). Consequently, various nanoparticles of anatase and rutile TiO2, characterized by well-defined morphologies, were synthesized. In the case of the anatase samples, bipyramids, needles, and cubes were obtained. For the rutile samples, all exhibited a needle-like shape, featuring {110} facets along the long direction of the needles and facets {111} on the upper and lower parts. Phosphate adsorption experiments carried out at pH 2 revealed that the maximum adsorption was relatively consistent across all samples, averaging around 1.5 phosphatenm-2 in all cases. Experiments using infrared spectroscopy on dried TiO2 powders showed that phosphates were chemisorbed on the surfaces and that the mode of adsorption depended on the crystalline phase and the nature of the facet: the anatase phase favors bidentate adsorption more than the rutile crystalline phase.

We investigate the contribution of pseudocapacitance to the overall capacitance of MnO2 electrodes in pure and alkaline-doped ionic liquids via two spectroscopic methods: step potential electrochemical spectroscopy (SPECS) and in situ Raman spectroscopy. For both characterization methods, thin-film electrodes of birnessite-like amorphous MnO2 were cycled in Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, pure or doped with lithium or sodium. SPECS allows determination of the influence of the electrolyte composition on the electrochemical behavior of the MnO2 electrodes. Pseudocapacitive charge storage can account for over half of the total capacitance with alkaline-doped ionic liquids. In situ Raman spectroscopy provided insight into the reversible ion intercalation in the MnO2 structure, which appears to be controlled by EMIm+ cations. These findings are supported by density functional theory (DFT) calculations, which further help unveil the charge storage mechanism in birnessite-like amorphous MnO2 thin films operated in pure and alkaline-doped ionic liquids.

Tricalcium phosphate (TCP) is a food additive, labeled E341(iii), used in powdered food preparation, such as baby formula. In the United States, calcium phosphate nano-objects were identified in baby formula extractions. Our goal is to determine whether the TCP food additive, as is used in Europe, can be classified as a nanomaterial. The physicochemical properties of TCP were characterized. Three different samples (from a chemical company and two manufacturers) were thoroughly characterized according to the recommendations of the European Food Safety Authority. A commercial TCP food additive was identified as actually being hydroxyapatite (HA). It presents itself in the form of particles of different shapes (either needle-like, rod, or pseudo-spherical), which were demonstrated in this paper to be of a nanometric dimension: E341(iii) is thus a nanomaterial. In water, HA particles sediment rapidly as agglomerates or aggregates over a pH of 6 and are progressively dissolved in acidic media (pH < 5) until the complete dissolution at a pH of 2. Consequently, since TCP may be considered as a nanomaterial on the European market, it raises the question of its potential persistency in the gastrointestinal tract.

The Light-Induced Excited Spin-State Trapping (LIESST) process allows tuning the electronic state of spin crossover materials from low (LS) to high spin (HS) states. The photoinduced HS state is long-lived, up to a characteristic temperature, T(LIESST), above which the system relaxes rapidly to the LS state. We study the effect of light irradiance on competing LS & nbsp;-> HS up-conversion and HS -> LS thermal relaxation on the [Fe (phen)(2)(NCS)(2)] system. Raman spectroscopy and magnetic measurements are used to investigate this phenomenon. An empiric model describes the competition between up conversion and thermal relaxation mechanisms and the stabilization of photo-stationary state towards higher temperature.

In the family of spin-crossover materials, which undergo thermal conversion between low-spin (LS) and high-spin (HS) phases, it is of great interest to study vibrational modes. On the one hand, vibration modes are characteristic of the spin state, and vibrational spectroscopies are often used for monitoring spin-state switching driven by temperature, pressure, or light. On the other hand, spin-state thermal conversion is an entropy-driven process, and the vibrational entropy change represents the main contribution to the total entropy difference between LS and HS phases at solid state. However, the discussion of vibrations in spin-crossover materials is often limited at the molecular scale. Here we study vibration modes in the [Fe(phen)(2)(NCS)(2)] crystal, and we compare symmetry-resolved vibrational spectroscopy data performed on single crystal to density functional theory calculations performed in a periodic three-dimensional crystal. We discuss the complex nature of vibrational modes in crystals, including the vibration of molecules within the crystalline lattice, with different symmetries and frequencies. We also highlight the presence of many low-frequency libration modes of different symmetries. The contribution of vibrational entropy, added to the electronic entropy, provides a total entropy difference in the solid state, which is in very good agreement with calorimetric measurements.

Among all potential active materials for the anodes of Li-ion batteries, silicon is considered as one of the most promising candidate because of its high specific and volumetric capacities, about 3600 mAh.g-1 and 2200 mAh.cm-3 respectively,1 as well as its low operation voltage (0.4 versus Li/Li+), abundant resources (the second largest in the earth’s crust), and environmental benignity (non-toxic). However, during the lithiation (formation of LixSi, x ~ 3.75) the silicon undergoes an expansion of about 280% of its initial volume2 which induces numerous damages to the electrode. The silicon micrometer particles tend to be pulverized when the size of the particles are upper than 150 nm.3 However, nanosizing the materials leads to more electrolyte degradation due to a higher specific surface developed and requires more binder and eventually more conducting additive in the electrode formulation. The pulverized Si particles are scattered and become electrically isolated and the adhesion of the Si electrode to the current collector are also damaged by these volume variations4. This effects drastically reduces the electrochemical performance and lifetime of the Si electrode. As a result, these challenges have seriously restricted the commercialization of Si anodes in high energy LIBs.5 To deal with these problems many researches are developing advanced binders. This later has a crucial role since it reinforces the mechanical strength of the electrode and thus helps to preserve the electrode architecture upon cycling against the large Si volume change.6 It is generally accepted that binders of very high molar masses (polymers) are necessary to allow cycling of silicon-based electrodes, as they favor the formation of more robust molecular bridges and therefore are a priori more capable of maintaining particle-to-particle contacts and therefore cohesion in the electrode. Quite surprisingly, we have discovered that it is possible to obtain good cyclability of silicon-based electrodes by using an organic binder of low molar mass (molecule). This calls into question the understanding of the mechanism by which the binder operates in silicon-based electrodes. This low molecular weight binder is a natural polyphenol, namely tannic acid. Here we will highlight that Silicon-based composite electrodes of high areal capacity (~7 mAh.cm-2) when prepared with tannic acid as small binder show a stable cycling like the one obtained with one state-of-the-art binder such as carboxymethyl cellulose. We will report in-depth characterization of the interactions between tannic acid and the silicon particles surface as well as of the rheological behavior of the electrode slurries and the electrodes properties and electrochemical performances. References (1) Obrovac, M. N.; Chevrier, V. L. Alloy Negative Electrodes for Li-Ion Batteries. Chem. Rev. 2014, 114 (23), 11444–11502. (2) Jung, S. C.; Choi, J. W.; Han, Y.-K. Anisotropic Volume Expansion of Crystalline Silicon during Electrochemical Lithium Insertion: An Atomic Level Rationale. Nano Lett. 2012, 12 (10), 5342–5347. (3) Liu, X. H.; Zhong, L.; Huang, S.; Mao, S. X.; Zhu, T.; Huang, J. Y. Size-Dependent Fracture of Silicon Nanoparticles During Lithiation. ACS Nano 2012, 6 (2), 1522–1531. (4) Hernandez, C. R.; Etiemble, A.; Douillard, T.; Mazouzi, D.; Karkar, Z.; Maire, E.; Guyomard, D.; Lestriez, B.; Roué, L. A Facile and Very Effective Method to Enhance the Mechanical Strength and the Cyclability of Si-Based Electrodes for Li-Ion Batteries. Adv. Energy Mater. 2018, 8 (6), 1701787. (5) Ko, M.; Chae, S.; Cho, J. Challenges in Accommodating Volume Change of Si Anodes for Li-Ion Batteries. ChemElectroChem 2015, 2 (11), 1645–1651. (6) Eshetu, G. G.; Figgemeier, E. Confronting the Challenges of Next-Generation Silicon Anode-Based Lithium-Ion Batteries: Role of Designer Electrolyte Additives and Polymeric Binders. ChemSusChem 2019, 12 (12), 2515–2539.

This multi-scale and multi-technique work investigates the adsorption of phosphated species on the TiO2 anatase surface. Our original approach declines for the first time the progressive ethyl substitution of phosphates to identify the structure of complexes formed upon adsorption of these molecules on anatase in aqueous dispersions, under various pH conditions. To quantify the adsorbed amount of these molecules on TiO2, adsorption isotherms were recorded as a function of pH. In parallel, zeta potential measurements were performed to screen the evolution of the TiO2 surface charge in the presence of the phosphated compounds. Lastly, surface complexes structure was characterized using spectroscopic methods: solid-state 31P Nuclear Magnetic Resonance, Attenu-ated Total Reflectance Fourier Transform Infrared, and Diffuse Reflectance Infrared Fourier Transform Spec-troscopy in the near infrared spectral range. Upon decreasing pH, the amount of adsorbed species increases, reaching a maximum of 1.5 phosphorus atom per nm2 at pH 2. Monoethyl-phosphate remains adsorbed in similar amounts to orthophosphate, but di-and tri-ethyl substitutions lead to a sharp decrease of adsorption. Spectro-scopic analyses reveal the affinity of othophosphate and monoethyl-phosphate for the anatase surface, with formation of bridging or chelating bidentate complexes, more or less protonated according to pH values.

The development of instruments combining multiple characterization and imaging tools drove huge advances in material science, engineering, biology, and other related fields. Notably, the coupling of SEM with micro-Raman spectrometry (μRaman) provides the means for the correlation between structural and physicochemical properties at the surface, while dual focused ion beam (FIB)-scanning electron microscopes (SEMs) operating under cryogenic conditions (cryo-FIB-SEM) allow for the analysis of the ultrastructure of materials in situ and in their native environment. In cryo-FIB-SEM, rapid and efficient methods for assessing vitrification conditions in situ are required for the accurate investigation of the original structure of hydrated samples. This work reports for the first time the use of a cryo-FIB-SEM-μRaman instrument to efficiently assess the accuracy of cryo-fixation methods. Analyses were performed on plunge-freezed highly hydrated calcium phosphate cement (CPC) and a gelatin composite. By making a trench of a defined thickness with FIB, μRaman analyses were carried out at a specific depth within the frozen material. Results show that the μRaman signal is sensitive to the changes in the molecular structures of the aqueous phase and can be used to examine the depth of vitreous ice in frozen samples. The method presented in this work provides a reliable way to avoid imaging artifacts in cryo-FIB-SEM that are related to cryo-fixation and therefore constitutes great interest in the study of vitreous materials exhibiting high water content, regardless of the sample preparation method (i.e., by HPF, plunge freezing, and so on).

Surface-enhanced Raman scattering (SERS) substrates consisting of stacked ultrathin nanoporous gold layers are used to detect very low concentrations of molecules in liquids or gases. The SERS substrates are obtained by copper chemical etching of alternative copper and gold stacked nanolayers. This process is a reliable method for fabricating uniform and reproducible SERS substrates, with a robust SERS response at extremely low detection limits. By optimizing fabrication conditions combined with a thorough analysis of the SERS mappings and using 2,2-bipyridine (BP) as probe molecules, the detection threshold corresponding to a detectable SERS response reaches a BP concentration of 10-18 mol center dot L-1 in water. An additional Raman mechanism is also highlighted by mu-surface enhancement spatially offset Raman spectroscopy (mu-SESORS): gold ligaments, inside nanoporous layers, act as waveguides for the incident light, leading to a significant increase in the size of the active SERS area. Moreover, these SERS substrates could be stored for several days without a significant decrease in their properties, and they can be reactivated and reused after SERS analysis. The ability to detect low BP vapor pressure is also demonstrated.

Li-ion batteries are growing in demand and such growth calls for the quest for high-energy-density electrode materials. Li-rich layered oxides that show both cationic and anionic redox are expected to meet the high energy requirement. However, the oxygen anion activity triggers numerous structural and electronic rearrangements that need to be understood prior to envisioning applications. Here, we chemically design two new LixIrS2 polymorphs to further interrogate the mechanisms of the ligand redox process. By combined structural and spectroscopic characterizations, we show that electrochemical lithiation/delithiation of the polymorphs involve different sulfur redox couples that stand as unusual behavior. These structure-dependent kinetic pathways lead to an similar to 1 V difference between the two polymorphs, hence providing the missing link between the structure and hysteresis in anionic redox systems. These insights into the origin of hysteresis can guide proper parameters to cure it, hence laying the groundwork for the design of new practical electrode materials.

In line with the SHINERS approach, in which Raman amplification is provided by metallic nanoparticles with an ultrathin dielectric shell, we report on a SERS substrate consisting of lines of Ag nanoparticles embedded in dielectric surfaces.

Green plasmon excitation of colloidal Au nanoparticles, onto which a copper( ii ) complex was grafted, in the presence of nitrobenzaldehyde and nitromethane in DMF, lead to the formation of the corresponding nitroaldol with high efficiency.